Insert for a flow through heater

ABSTRACT

When feedback loop control is used for controlling a temperature of liquid at an outlet ( 5 ) of a flow through heater, a volume of an ineffective portion ( 4 ) of the flow through heater at the outlet ( 5 ) constitutes a dead volume which causes a delay in the feedback process. In order to minimize the delay, an insert ( 6 ) is applied, which serves for reducing the dead volume by occupying most of this volume. In a practical case, the insert ( 6 ) comprises a duct system ( 12 ) for conveying liquid from a liquid conveying conduit ( 2 ) of the flow through heater to an outlet ( 10 ) of the insert ( 6 ). Preferably, a volume of such a liquid conveying duct system ( 12 ) is relatively small, so that the presence of the duct system ( 12 ) in the insert ( 6 ) does not spoil the dead volume reducing effect of the application of the insert ( 6 ).

FIELD OF THE INVENTION

The present invention relates to a device for heating liquid, comprisinga flow through heater having a conduit for conveying liquid and meansfor heating the liquid while flowing through the conduit; and means fordetecting a temperature of liquid at an outlet of the flow throughheater, which are part of a device for controlling a temperature ofliquid at the outlet of the flow through heater. Furthermore, thepresent invention relates to a method for increasing accuracy incontrolling a temperature of liquid at an outlet of a flow throughheater.

BACKGROUND OF THE INVENTION

In many types of devices, there is a need for means which are capable ofheating a quantity of liquid to be used during operation of the device.For example, in a device which is suitable for making hot coffee, aquantity of water is heated before being made to flow through a quantityof ground coffee beans.

For the purpose of heating a liquid such as water, many devices areequipped with a boiler, i.e. a device having a container for containinga quantity of liquid, and heating means which are associated with thecontainer, and which serve for heating liquid that is present inside thecontainer. As soon as the temperature of the liquid is at a desiredlevel, the liquid may be drawn from the boiler and used for its intendedpurpose. However, the application of a boiler has some notabledisadvantages, and therefore, another way of heating liquid has beendeveloped, which involves the application of a flow through heater, i.e.a device having a conduit for conveying liquid and means for heating theliquid while flowing through the conduit. In practical embodiments ofthe flow through heater, electric heating elements are arranged aroundthe liquid conveying conduit. Some important advantages of applying aflow through heater are that the heating process of the liquid isperformed almost instantaneously, so that there is hardly any waitingtime, that less energy is needed when compared to the application of aboiler, and that the flow through heater is not only suitable to be usedas a substitute of the boiler, but also in high pressure systems such asespresso devices.

For the purpose of controlling a temperature of liquid at an outlet ofthe flow through heater, a feed back control loop is likely to be used.However, in practice, it appears to be difficult or even impossible tomeet high demands in respect of the outlet temperature as mentioned. Inother words, it appears to be difficult or even impossible to controlthe operation of the flow through heater on the basis of a detection ofthe outlet temperature in a sufficiently accurate manner.

SUMMARY OF THE INVENTION

It is an object of the present invention to optimize the feedbackcontrol loop in a device comprising a flow through heater and thefeedback control loop for controlling the outlet temperature. The objectis achieved by providing an insert which is partially inserted in theliquid conveying conduit of the flow through heater, at an outlet sideof the flow through heater, wherein a portion of the insert that islocated inside the liquid conveying conduit of the flow through heateris occupying at least a substantial portion of space which is present ina portion of the liquid conveying conduit which is not directlyassociated with the heating means of the flow through heater.

According to an insight underlying the present invention, thedifficulties in controlling the outlet temperature are caused by a delayin the feedback process, which is related to the usual design of theflow through heater. In particular, in this design, the liquid conveyingconduit and the heating elements are arranged with respect to each otherin such a way that the conduit is protruding over some length withrespect to the heating elements, at both an inlet side and an outletside of the flow through heater. Hence, when the temperature of liquidis detected at the outlet of the flow through heater, which is in factthe outlet of the conduit, there is a delay caused by the fact that theliquid has first traveled through a length of the conduit which is notdirectly associated with heating elements before reaching the placewhere the detection takes place. In the following, this phenomenon willbe referred to as the presence of dead volume in the flow throughheater, and the portion of the conduit which is not directly associatedwith heating elements is referred to as ineffective portion of the flowthrough heater.

With respect to the dead volume and the associated delay time, it isnoted that the larger the dead volume, the harder it is to realize adesired average outlet temperature under all circumstances. This isespecially apparent when the dead volume is significant when compared toa total volume of the flow through heater, which is the case in flowthrough heaters which are suitable to be used in espresso devices, forexample. In general, the longer the delay time, the slower the responseof a feedback control loop, and the earlier an occurrence ofinstability. Therefore, a longer delay time leads to a restriction ofthe applicability of the flow through heater. For example, anapplication in an espresso device is practically not possible, as suchan application requires a fast responding feedback control loop.

In many applications, it is important to have the lowest possiblemanufacturing costs. Therefore, in many cases, it is not a feasibleoption to change the design of the flow through heater in order to solvethe above-sketched problems. Instead, another solution is needed on thebasis of the assumption that conventional flow through heaters areapplied. The present invention provides such solution by proposing theapplication of an insert which is partially inserted in the liquidconveying conduit of the flow through heater, at an outlet side of theflow through heater, wherein a portion of the insert that is locatedinside the liquid conveying conduit of the flow through heater isoccupying at least a substantial portion of the dead volume.

When the insert according to the present invention is applied, it isachieved that the dead volume is significantly reduced. This is due tothe fact that the portion of the insert that is located inside theliquid conveying conduit of the flow through heater fills up the deadvolume. In many practical cases, this portion of the insert is longerthan necessary for keeping the insert in place in the liquid conveyingconduit, as seen in a flow direction of liquid in the flow throughheater.

Due to the reduction of the dead volume which is achieved by applyingthe insert as mentioned, the delay time in detecting the outlettemperature of liquid is significantly reduced, as an advantageousresult of which controlling the outlet temperature can be performed moreeffectively and accurately. According to the present invention, it doesnot take a modification of the design of the flow through heater, nordoes it take an upgrade of the components used in the temperaturecontrolling process to achieve such an advantageous result, but it onlytakes the application of a simple additional component, namely theinsert.

In order to reduce the dead volume of the ineffective portion of theflow through heater as much as possible, and in order to have a securearrangement of the insert in the conduit, it is preferred if only littleplay is present between the inner surface of the liquid conveyingconduit of the flow through heater and the outer surface of the portionof the insert that is located inside the liquid conveying conduit.

In a practical case, the insert comprises a duct system for conveyingliquid from the liquid conveying conduit of the flow through heater toan outlet of the insert. In that case, the duct(s) of the liquidconveying duct system of the insert serve for transporting the liquidthrough the ineffective portion of the flow through heater. Preferably,a diameter of the duct(s) of such a liquid conveying duct system issignificantly smaller than a diameter of the liquid conveying conduit ofthe flow through heater at the outlet of the flow through heater, sothat the volume of the duct(s) is much smaller than the volume of theineffective portion of the flow through heater, and the dead volumereducing effect of the application of the insert may be optimal.

The insert according to the invention may comprise a duct which isextending from an outer surface of the insert to the liquid conveyingduct system, in a portion of the insert that is located outside of theliquid conveying conduit of the flow through heater, wherein the meansfor detecting a temperature of liquid at the outlet of the flow throughheater are associated with this duct. Preferably, this duct is locatedas close as possible to the end of the liquid conveying duct of the flowthrough heater, so that the detection of the outlet temperature may takeplace at a location which is as close as possible to the end of theliquid conveying duct, and the length over which a dead volume exists,albeit a relatively small dead volume, is kept to a minimum.

With respect to the liquid conveying duct system which may be part ofthe insert it is noted that this duct system may comprise at least twoducts which are oriented at an angle with respect to each other. In anadvantageous design, the duct system comprises at least one duct forletting in liquid to the duct system, wherein this at least one inletduct is oriented substantially perpendicular to a flow direction ofliquid in the flow through heater, and is extending from one side of theinsert to another; and a duct for letting out liquid from the ductsystem, wherein this outlet duct is oriented substantially parallel tothe flow direction of liquid in the flow through heater, and wherein theat least one inlet duct and the outlet duct are connected to each other.

An advantage of applying a design of the liquid conveying duct system ofthe insert in which the at least one inlet duct is oriented at an angleto the outlet duct, and in which the inlet duct is extending from oneside of the insert to another is that a situation in which liquid mightremain at an outlet of the insert is prevented. The inlet duct functionsas a kind of shortcut, and liquid cannot reach the outlet of the insertunless a sucking and/or pressing force is applied. Furthermore, it ispossible to create various inlet passages when the concept of having anangle between the inlet duct(s) and the outlet duct is applied, so thatmixing of the liquid is realized at the connection of the inlet duct(s)to the outlet duct, which results in an even more accurate temperaturedetection.

In a practical embodiment, in particular an embodiment in which theinsert comprises a liquid conveying duct system, the device according tothe present invention may further comprise means for sealing a spacebetween an outer surface of a portion of the insert that is locatedinside the liquid conveying conduit of the flow through heater and aninner surface of the liquid conveying conduit. By using suitable sealingmeans, leakage of liquid from the liquid conveying conduit through a(narrow) space between the outer surface of the insert and the innersurface of the conduit is prevented. Naturally, the sealing means, whichmay comprise an O-ring or the like, are located behind the inlet(s) ofthe liquid conveying duct system of the insert as seen in the flowdirection of liquid in the flow through heater.

Many of the above-described aspects of the present invention appear fromthe insert when being considered separately. In that case, these aspectsare worded as follows.

The insert is described in general as an insert which is intended foruse in the device for heating liquid as described in the foregoing,comprising:

-   -   an end portion which is suitable to be inserted in a conduit for        conveying liquid, in particular a liquid conveying conduit which        is part of a flow through heater further having means for        heating liquid while flowing through the conduit; and    -   a duct system for conveying liquid through the insert, wherein a        diameter of the duct(s) of the liquid conveying duct system is        significantly smaller than an outer diameter of the end portion.

In the insert according to the present invention, it is advantageous ifthe liquid conveying duct system comprises at least two ducts which areoriented at an angle with respect to each other. Preferably, in thatcase, the liquid conveying duct system comprises at least one duct forletting in liquid to the duct system, wherein this at least one inletduct is oriented substantially perpendicular to an axial direction ofthe insert, i.e. a longitudinal direction of the insert, and isextending from one side of the insert to another; and a duct for lettingout liquid from the duct system, wherein this outlet duct is orientedsubstantially parallel to the axial direction of the insert, and whereinthe at least one inlet duct and the outlet duct are connected to eachother.

For the purpose of allowing temperature detection of liquid at theinside of the insert, it is advantageous if the insert further comprisesa duct which is extending from an outer surface of the insert to theliquid conveying duct system, in another portion of the insert than theend portion which is suitable to be inserted in a conduit for conveyingliquid.

The sealing means which are preferably used for avoiding leakage ofliquid from the liquid conveying conduit of the flow through heater maybe provided as (a) component(s) of the insert. In such a case, theinsert further comprises means such as an O-ring which are suitable tobe used for sealing a space between two surfaces, wherein these sealingmeans are located at the end portion which is suitable to be inserted ina conduit for conveying liquid.

Besides a device for heating a liquid as described in the foregoing, thepresent invention also provides a method for increasing accuracy at anoutlet of a flow through heater having a conduit for conveying liquidand means for heating the liquid while flowing through the conduit,wherein at least a substantial portion of space which is present in aportion of the liquid conveying conduit of the flow through heater whichis not directly associated with the heating means of the flow throughheater is filled up by providing an insert and introducing at least aportion of the insert in the liquid conveying conduit into the flowthrough heater, at an outlet side of the flow through heater.

Preferably, when the method according to the present invention iscarried out, only little play is allowed between an inner surface of theliquid conveying conduit of the flow through heater and an outer surfaceof the portion of the insert that is inserted in the liquid conveyingconduit.

The insert which is applied when the method according to the presentinvention is carried out, may be the insert as defined in the foregoing,or any other suitable insert, provided that a reduction of the deadvolume can be achieved through an occupation of this volume, and that aflow of liquid is not blocked.

The above-described and other aspects of the present invention will beapparent from and elucidated with reference to the following detaileddescription of an embodiment of the insert according to the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in greater detail withreference to the figures, in which equal or similar parts are indicatedby the same reference signs, and in which:

FIG. 1 diagrammatically shows a flow through heater;

FIG. 2 diagrammatically shows a portion of a flow through heater and aninsert according to the present invention;

FIGS. 3 and 4 show views of two longitudinal sections of an end of aliquid conveying conduit of the flow through heater and the insert.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 diagrammatically shows a flow through heater 1 as known in theart. In general, the flow through heater 1 comprises a conduit 2 forconveying liquid and heating elements 3 which are arranged such as toclosely surround the liquid conveying conduit 2. In most cases, across-sectional area of the liquid conveying conduit has a circularshape, which does not alter the fact that other shapes are possible aswell.

In FIG. 1, it can clearly be seen that not all of the length of theliquid conveying conduit 2 is covered by the heating elements 3. At bothan inlet side and an outlet side of the flow through heater 1, a length4 of the liquid conveying conduit 2 is not directly associated with theheating elements 3. These lengths 4 are referred to as ineffectiveportions 4 of the flow through heater 1.

During operation of the flow through heater 1, a liquid such as water ismade to flow through the liquid conveying conduit 2, while the heatingelements 3 are operated for supplying heat to the liquid in order toachieve an increase of the temperature of the liquid. Three importantfactors in achieving a desired temperature of the liquid at an outlet 5of the flow through heater 1 are the initial temperature of the liquid,the flow rate, and the supply of heat. In order to check whether anactual outlet temperature of liquid is within a desired range, and todetermine whether parameters of the flow through heating process such asa power supply to the heating elements 3 of the flow through heater 1need to be adjusted, it is common practice to have a feedback controlloop, wherein the outlet temperature is detected and used as a basis forpossible adjustments. However, due to the presence of an ineffectiveportion 4 at the outlet of the liquid conveying conduit 2 of the flowthrough heater 1, there is a delay in the feedback control loop, whichhas a negative influence on the accuracy of the temperature controllingprocess.

The delay in the feedback control loop is directly related to the volumeof the ineffective portion 4 at the outlet of the flow through heater 1,which is referred to as dead volume. For example, when the ineffectiveportion 4 has a length of 2 cm, an inner diameter of the liquidconveying conduit 2 is 1 cm, the flow rate is 5 ml/s and the outlettemperature is detected at the outlet 5 of the flow through heater 1,the delay time appears to be 0.314 s. This value is found by determiningthe dead volume, and dividing the dead volume by the flow rate. The deadvolume equals pi*r²*l=pi*0.5²*2=1.57 ml, wherein r stands for the innerradius of the liquid conveying conduit 2, and wherein l stands for thelength of the ineffective portion 4 of the flow through heater 1. Hence,the delay time equals 1.57/5=0.314 s. For example, for applicationsrelated to making espresso, a dead volume of 1.57 ml is significantcompared to a total volume. Therefore, in such cases, the dead volumehas a significant influence on a final temperature of the beverage.

In order to minimize the delay in the feedback control loop, the presentinvention proposes measurements to make the dead volume as small aspossible. These measurements involve the application of an insert 6which is partially inserted in the liquid conveying conduit 2 of theflow through heater 1, as is illustrated by FIG. 2 in which the insert 6is indicated by dashed lines. Furthermore, FIG. 2 indicates anappropriate position of a temperature sensor 7, which is in a portion ofthe insert 6 right outside of the flow through heater 1. The insert 6 ispreferably designed such as to remove as much of the dead volume aspossible, while at the same time allowing for a required flow of liquid.The design of the insert 6 will be further elucidated on the basis ofFIGS. 3 and 4, in which longitudinal sections of the insert 6 are shown,as well as a portion of the liquid conveying conduit 2 of the flowthrough heater 1, in which the insert 6 is partially inserted.

The example of the insert 6 as shown in FIGS. 3 and 4 comprises threeportions. A first portion 8 is an end portion which is suitable to belocated inside the ineffective portion 4 of the flow through heater 1.Hence, an outer diameter of this end portion 8 of the insert 6 issmaller than an inner diameter of the liquid conveying conduit 2 of theflow through heater 1. A second portion 9 is another end portion whichallows for connection of a hose or the like to the insert 6, and has anoutlet 10 for the liquid at its free end. A third portion 11 is anintermediate portion which is intended to be arranged such as to abutagainst an end of the liquid conveying conduit 2 of the flow throughheater 1. Hence, an outer diameter of this intermediate portion 11 ofthe insert 6 is larger than an inner diameter of the liquid conveyingconduit 2 of the flow through heater 1.

Inside the insert 6, a duct system 12 for conveying liquid through theinsert 6 is arranged. At an inlet side, i.e. a side closest to the flowthrough heater 1, the duct system 12 comprises two ducts 13 a, 13 bwhich are extending in a radial direction of the insert 6, i.e. adirection perpendicular to a flow direction of liquid in the flowthrough heater 1. These ducts 13 a, 13 b serve for letting in liquid tothe insert 6 and conveying the liquid to a central location inside theinsert 6 where the ducts 13 a, 13 b are crossing. Extending from thislocation to the outlet 10 of the insert 6, an outlet duct 14 is presentinside the insert 6. For sake of completeness, it is noted that the flowdirection of liquid in the flow through heater 1 is indicated by meansof arrows in the figures.

It should be clear that other designs than the above-described design ofthe liquid conveying duct system 12 of the insert 6 are possible withinthe scope of the present invention. For example, there could be asingle, central duct extending through the insert 6. However, theconfiguration with the radially oriented inlet ducts 13 a, 13 b ispreferred, as it is possible to avoid a situation in which liquid is notrefreshed and remains at an outlet side of the insert 6 when thisconfiguration is realized. This is important in view of the fact that aremaining quantity of liquid can be a source of bacteria growth.Furthermore, by letting in liquid from various sides of the insert 6,mixing of the liquid is achieved, which contributes to a smoothtemperature detection.

Besides ducts 13 a, 13 b, 14 for conveying liquid, the insert 6 has aduct 15 for accommodating one or more components or portions ofcomponents (now shown in FIGS. 3 and 4) which are to be used in aprocess of detecting the outlet temperature of liquid. In the following,this duct 15 will be referred to as detection duct 5. The detection duct15 is arranged in the intermediate portion 11 of the insert 6, and isextending from an outer surface of the insert 6 to the outlet duct 14,in order to allow free access of the detection component(s) to liquidflowing through the outlet duct 14. In the shown example, the detectionduct 15 has a radial orientation in the insert 6, like the inlet ducts13 a, 13 b.

For the purpose of avoiding leakage of liquid from the liquid conveyingconduit 2 of the flow through heater 1, sealing means are arrangedbetween an inner surface of the conduit 2 and the outer surface of theinsert 6, at a position behind the position where the inlet ducts 13 a,13 b of the insert 6 are located. Within the scope of the presentinvention, any suitable type of sealing means may be applied. In theshown example, the sealing means comprise an O-ring 16 which isaccommodated in a groove that is arranged in the outer surface of theinsert 6.

FIGS. 3 and 4 show that the dimensions of the end portion 8 of theinsert 6 which is suitable to be located inside the ineffective portion4 of the flow through heater 1 are chosen such that only minimal spaceis present between an outer surface of this portion 8 of the insert 6and the inner surface of the liquid conveying conduit 2 of the flowthrough heater 1 when the insert 6 is in its proper position. All inall, when the insert 6 is put in place at the outlet side of the flowthrough heater 1, most of the volume of the ineffective portion 4 of theflow through heater 1 is filled up, wherein the volume causing delay inthe detection of the outlet temperature of liquid is no more than avolume which is the sum of the space which is present between the outersurface of the inserted portion 8 of the insert 6 and the inner surfaceof the liquid conveying conduit 2 of the flow through heater 1, thevolume of the inlet ducts 13 a, 13 b of the insert 6, and the volume ofthe outlet duct 14 between the connection to the inlet ducts 13 a, 13 band the position of the detection duct 15.

It is most advantageous if the diameters of the ducts 13 a, 13 b, 14 ofthe liquid conveying duct system 12 of the insert 6 are significantlysmaller than the diameter of the liquid conveying conduit 2 of the flowthrough heater 1 at the outlet side of the flow through heater 1, sothat the dead volume can actually be as small as possible. Due to thereduction of the dead volume of the ineffective portion 4 of the flowthrough heater 1, the present invention allows for an improved way ofcontrolling the outlet temperature, which results in better performancesof the devices in which the invention will be applied. Examples of suchdevices which are worthy of mention here are beverage making devices, inparticular coffee devices and espresso devices of various types,including the drip filter type and the pad processing type, and babymilk devices.

During a manufacturing process of a device in which the presentinvention is applied, a conventional flow through heater 1 is provided,wherein the dead volume at the outlet side of the flow through heater 1is reduced by providing the insert 6 according to the present inventionand introducing the end portion 8 of the insert 6 into the liquidconveying conduit 2 of the flow through heater 1.

It will be clear to a person skilled in the art that the scope of thepresent invention is not limited to the examples discussed in theforegoing, but that several amendments and modifications thereof arepossible without deviating from the scope of the present invention asdefined in the attached claims. While the present invention has beenillustrated and described in detail in the figures and the description,such illustration and description are to be considered illustrative orexemplary only, and not restrictive. The present invention is notlimited to the disclosed embodiments.

Variations to the disclosed embodiments can be understood and effectedby a person skilled in the art in practicing the claimed invention, froma study of the figures, the description and the attached claims. In theclaims, the word “comprising” does not exclude other steps or elements,and the indefinite article “a” or “an” does not exclude a plurality. Themere fact that certain measures are recited in mutually differentdependent claims does not indicate that a combination of these measurescannot be used to advantage. Any reference signs in the claims shouldnot be construed as limiting the scope of the present invention.

The present invention can be summarized as follows. In a flow throughheater 1 of common design, an effective portion and two ineffectiveportions 4 located at ends of the flow through heater 1 can bediscerned, wherein the ineffective portions 4 are portions where aliquid conveying conduit 2 of the flow through heater 1 is not directlyassociated with heating means 3 of the flow through heater 1. Whenfeedback loop control is used for controlling a temperature of liquid atan outlet 5 of the flow through heater 1, a volume of the ineffectiveportion 4 at the outlet 5 constitutes a dead volume which causes a delayin the feedback process, resulting in instability and inaccuracy of thetemperature control. In order to prevent this, the delay should beminimized. Therefore, it is desired to detect the outlet temperature asquick as possible after the effective portion of the flow through heater1 as seen in a flow direction of liquid in the flow through heater 1.This is realized by applying an insert 6 for reducing the dead volume byoccupying most of this volume. In a practical case, the insert 6comprises a duct system 12 for conveying liquid from the liquidconveying conduit 2 of the flow through heater 1 to an outlet 10 of theinsert 6. Preferably, in such a case, a diameter of the duct(s) 13 a, 13b, 14 of the liquid conveying duct system 12 is significantly smallerthan a diameter of the liquid conveying conduit 2 of the flow throughheater 1 at the outlet 5 of the flow through heater 1, so that a volumeof the liquid conveying duct system 12 is relatively small, and thepresence of the duct system 12 in the insert 6 does not spoil the deadvolume reducing effect of the application of the insert 6.

1. Device for heating liquid, comprising: a flow through heater (1)having a conduit (2) for conveying liquid and means (3) for heating theliquid while flowing through the conduit (2); means (7) for detecting atemperature of liquid at an outlet (5) of the flow through heater (1),which are part of a device for controlling a temperature of liquid atthe outlet (5) of the flow through heater (1); and an insert (6) whichis partially inserted in the liquid conveying conduit (2) of the flowthrough heater (1), at an outlet side of the flow through heater (1),wherein a portion (8) of the insert (6) that is located inside theliquid conveying conduit (2) of the flow through heater (1) is occupyingat least a substantial portion of space which is present in a portion(4) of the liquid conveying conduit (2) which is not directly associatedwith the heating means (3) of the flow through heater (1).
 2. Deviceaccording to claim 1, wherein only little play is present between aninner surface of the liquid conveying conduit (2) of the flow throughheater (1) and an outer surface of the portion (8) of the insert (6)that is located inside the liquid conveying conduit (2).
 3. Deviceaccording to claim 1, wherein the insert (6) comprises a duct system(12) for conveying liquid from the liquid conveying conduit (2) of theflow through heater (1) to an outlet (10) of the insert (6), and whereina diameter of the duct(s) (13 a, 13 b, 14) of the liquid conveying ductsystem (12) is significantly smaller than a diameter of the liquidconveying conduit (2) of the flow through heater (1) at the outlet (5)of the flow through heater (1).
 4. Device according to claim 3, whereinthe liquid conveying duct system (12) of the insert (6) comprises atleast two ducts (13 a, 13 b, 14) which are oriented at an angle withrespect to each other.
 5. Device according to claim 4, wherein theliquid conveying duct system (12) of the insert (6) comprises at leastone duct (13 a, 13 b) for letting in liquid to the duct system (12),wherein this at least one inlet duct (13 a, 13 b) is orientedsubstantially perpendicular to a flow direction of liquid in the flowthrough heater (1), and is extending from one side of the insert (6) toanother; and a duct (14) for letting out liquid from the duct system(12), wherein this outlet duct (14) is oriented substantially parallelto the flow direction of liquid in the flow through heater (1), andwherein the at least one inlet duct (13 a, 13 b) and the outlet duct(14) are connected to each other.
 6. Device according to claim 3,wherein the insert (6) further comprises a duct (15) which is extendingfrom an outer surface of the insert (6) to the liquid conveying ductsystem (12), in a portion (11) of the insert (6) that is located outsideof the liquid conveying conduit (2) of the flow through heater (1), andwherein the means (7) for detecting a temperature of liquid at theoutlet (5) of the flow through heater (1) are associated with this duct(15).
 7. Device according to claim 3, further comprising means (16) forsealing a space between an outer surface of a portion (8) of the insert(6) that is located inside the liquid conveying conduit (2) of the flowthrough heater (1) and an inner surface of the liquid conveying conduit(2).
 8. Method for increasing accuracy in controlling a temperature ofliquid at an outlet of a flow through heater (1) having a conduit (2)for conveying liquid and means (3) for heating the liquid while flowingthrough the conduit (2), wherein at least a substantial portion of spacewhich is present in a portion (4) of the liquid conveying conduit (2) ofthe flow through heater (1) which is not directly associated with theheating means (3) of the flow through heater (1) is filled up byproviding an insert (6) and introducing at least a portion (8) of theinsert (6) into the liquid conveying conduit (2) of the flow throughheater (1), at an outlet side of the flow through heater (1).
 9. Methodaccording to claim 8, wherein only little play is allowed between aninner surface of the liquid conveying conduit (2) of the flow throughheater (1) and an outer surface of the portion (8) of the insert (6)that is inserted in the liquid conveying conduit (2).